Schematic Rev B12 & PCB Progress

[NZ0I]

A schematic for Rev B12 is now on the shared drive. Not many changes except to add support for using the IF Amplifier in the SA605. The design now includes two 10.7 MHz crystal filters. It also has support for three different ways to adjust the gain/attenuation - so hopefully we can get the gain control we need from one, or a combination of the methods. Also added another sheet to the schematic for capturing dual-band transmitter design ideas.

As always, if you find errors, omissions, or just have alternative ideas/observations please let me know.

The Dual-Band Receiver PCB has been laid out and traces run, and just doing some touch-up work on it before turning attention to the Digital Interface PCB.

[NZ0I]

Below is the Receiver Board. It passes muster at OSH Park, and passes all the design rules checks. It uses "solder blob" jumpers, which you can see if you examine the board carefully - they are all labeled JPxxx. It comes pre-jumpered for the default configuration. You can reconfigure it by cutting a trace shorting two jumper pads, then solder-short the middle pad to the alternative pad. AdaFruit has this on many of their boards, and it seems to work well. Since this is a 4-layer board I have removed all middle-layer traces and copper fill from beneath the jumpers where you would need to cut a trace - hopefully making it easy to avoid damaging underlying layers while cutting the trace.

The crystal filter footprints should be the right size, as they have been corrected since the first IF Board that Jerry built.

Some of the silk screen part annotations are really really small. I'm not certain that they will turn out legibly with OSH's silk screen process. I may try to enlarge them. Let me know if you think of other changes that might improve the board.

Top Side of ARDF 2-Band Rx Board

[NZ0I]

One more consideration for the Receiver Board: all the trimmer caps are on one side (the top) of the receiver board, so adjustments can be made with the board installed in the chassis box. Also, I've attempted to place all the trimmers so that they should be accessible even after the Digital Interface board is installed.

On Sunday, January 29, 2017 at 9:56:13 AM UTC-5, NZ0I wrote:

[Gerald Boyd]

That's a good plan. Making it easy for receiver alignment.

Looking at the schematics I wonder if the 80 meter loop module can be tested standalone using a portable hf shortwave receiver and ARDF transmitter? Some of the portable receivers nowadays have RF gain controls.

Also noticed the last sheet a start of an ARDF transmitter.

Jerry 

Sent from my iPhone

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[Charles Scharlau]

Yes! Actually I built a stand-alone 80m rod antenna that I used with my Icom IC-R10 to compete at the 2002? USA Championships in Georgia. It worked reasonably well - my biggest problem was that the R10 kept getting powered off when my fingers would bump the power button. The depth of the null of that antenna was not great, but it worked well enough to easily remove the 180-degree ambiguity. It used mechanical switches, not the PIN diode to engage the sense antenna. Also, I had to wrap the R10 in aluminum foil with cutouts for the buttons and display, in order to get adequate shielding.

I think this 80m antenna design can (with experimentation) be made to work as well as Russian receivers. And it can be attached to any 80m receiver, but you would need to use a standard mechanical switch, or add an external way to inject DC into the antenna center conductor.

The transmitter sheet is for capturing ideas for transmitter design and components. I'll be needing a dual-band transmitter to test the dual-band receiver at some point. I'm thinking that I might have some time to look at that while waiting for receiver boards from OSHPark.

On Mon, Jan 30, 2017 at 8:25 AM, Gerald Boyd <wb8...@icloud.com> wrote:

That's a good plan. Making it easy for receiver alignment.

Looking at the schematics I wonder if the 80 meter loop module can be tested standalone using a portable hf shortwave receiver and ARDF transmitter? Some of the portable receivers nowadays have RF gain controls.

Also noticed the last sheet a start of an ARDF transmitter.

Jerry 

Sent from my iPhone

On Jan 29, 2017, at 2:49 PM, NZ0I <charles....@gmail.com> wrote:

One more consideration for the Receiver Board: all the trimmer caps are on one side (the top) of the receiver board, so adjustments can be made with the board installed in the chassis box. Also, I've attempted to place all the trimmers so that they should be accessible even after the Digital Interface board is installed.

On Sunday, January 29, 2017 at 9:56:13 AM UTC-5, NZ0I wrote:

A schematic for Rev B12 is now on the shared drive. Not many changes except to add support for using the IF Amplifier in the SA605. The design now includes two 10.7 MHz crystal filters. It also has support for three different ways to adjust the gain/attenuation - so hopefully we can get the gain control we need from one, or a combination of the methods. Also added another sheet to the schematic for capturing dual-band transmitter design ideas.

As always, if you find errors, omissions, or just have alternative ideas/observations please let me know.

The Dual-Band Receiver PCB has been laid out and traces run, and just doing some touch-up work on it before turning attention to the Digital Interface PCB.

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[Charles Scharlau]

The other thing that this compact stand-alone 80m DF antenna might support: being mounted on top of a slip ring assembly: https://www.adafruit.com/products/736

I don't want to forget about the slip-ring possibility, since I think it would make 80m DFing much more intuitive, as well as more comfortable on the wrist. Twist the antenna itself broadside to hunt the null, then turn it front/back to hunt the peak. I think magnets mounted above and below the slip ring assembly might create stable 90-degree rotation "indents" for properly aligning the antenna. The same magnets might engage magnetic reed switches that engage/disengage the sense antenna appropriately. Thus, no batteries or DC-voltage injection required.

[NZ0I]

Here's the Digital Interface PCB. It passes the design rule checker, and passes muster when uploaded to OSH Park. BT101 at the near edge of the board is the footprint for the coin cell holder for the real-time clock backup battery - so the battery can be installed/removed from the top without removing the PCB from the chassis box. J102 is the footprint for the headphone jack - it should butt up against the side of the chassis box, and protrude into a hole drilled in it. 

On Sunday, January 29, 2017 at 9:56:13 AM UTC-5, NZ0I wrote:

[NZ0I]

Three boards are now mostly done: Receiver, Digital Interface, and Control Head. Updates were made to the Digital Interface: added a Micro USB connector (waterproof) next to the headphone jack, both will protrude into holes made in the chassis wall. You can still install the Micro USB connector on the Control Head instead if you prefer - just choose one or the other - it is for charging the LiPo only; no USB communication lines are connected. 

Also discovered that I needed to cut a corner off the Digital Interface board to prevent running into the chassis box wall. Below are 3D images of the two boards.

Control Head - Display Side

Digital Interface Board - Top Side

On Sunday, January 29, 2017 at 9:56:13 AM UTC-5, NZ0I wrote:

[NZ0I]

All four PCB boards are now done. The 80m DF Antenna board is shown below. I added a BNC connector at the bottom, and also through-holes for attaching a mechanical sense switch button, if you want to build it with a mechanical switch instead of the PIN diode switch. The DF antenna also has some solder-blob jumpers that could be used to reverse the direction of the cardioid pattern, in case we want to experiment with the slip-ring reed-switch approach in which the cardioid max direction is always kept in a forward direction. The board will fit inside this box: http://www.digikey.com/products/en?keywords=HM108-ND or any box of similar size, with only the coaxial cable loop antenna extending outside the box.

I've updated the schematic diagram (Rev B.15) to show the changes made to the 80m antenna, as well as various tweaks to the other boards. The updated schematic is now on the shared drive. 

I'll tweak the board designs for a few days, and then place orders with OSH Park.

80m ARDF Antenna Board

On Sunday, January 29, 2017 at 9:56:13 AM UTC-5, NZ0I wrote:

[Gerald Boyd]

Looks good.

Will have to update the presentation with the new images.

I had uploaded the presentation to the share site earlier today
Jerry
Sent from my iPad

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[Charles Scharlau]

I took a quick look at the updated presentation document. It is looking good. I wonder if we might want to move away from the "Motherboard" terminology, since our concept has evolved a bit from that? What the schematic now aims for is a "Receiver Board" with an "Interface Board" that allows you to connect a "Control Head" to the receiver. Like with the motherboard concept, the Digital Interface Board can be plugged into any project (not just receivers) requiring a processor, I2C, and up to 3 clock signals, and an audio amplifier. But there isn't really a motherboard into which you can plug front-end and IF daughter boards anymore. But I think that this new concept actually makes the entire project potentially more useful to more projects. 

On Sun, Feb 5, 2017 at 10:55 PM, Gerald Boyd <wb8...@icloud.com> wrote:

Looks good.

Will have to update the presentation with the new images.

I had uploaded the presentation to the share site earlier today
Jerry
Sent from my iPad

On Feb 4, 2017, at 12:22 PM, NZ0I <charles....@gmail.com> wrote:

Three boards are now mostly done: Receiver, Digital Interface, and Control Head. Updates were made to the Digital Interface: added a Micro USB connector (waterproof) next to the headphone jack, both will protrude into holes made in the chassis wall. You can still install the Micro USB connector on the Control Head instead if you prefer - just choose one or the other - it is for charging the LiPo only; no USB communication lines are connected. 

Also discovered that I needed to cut a corner off the Digital Interface board to prevent running into the chassis box wall. Below are 3D images of the two boards.

Control Head - Display Side

Digital Interface Board - Top Side

On Sunday, January 29, 2017 at 9:56:13 AM UTC-5, NZ0I wrote:

A schematic for Rev B12 is now on the shared drive. Not many changes except to add support for using the IF Amplifier in the SA605. The design now includes two 10.7 MHz crystal filters. It also has support for three different ways to adjust the gain/attenuation - so hopefully we can get the gain control we need from one, or a combination of the methods. Also added another sheet to the schematic for capturing dual-band transmitter design ideas.

As always, if you find errors, omissions, or just have alternative ideas/observations please let me know.

The Dual-Band Receiver PCB has been laid out and traces run, and just doing some touch-up work on it before turning attention to the Digital Interface PCB.

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